On Fri, 28 Apr 2023 at 08:34, Jakub Jelinek wrote: > Hi! > > GCC used to emit an instance of an empty ios_base::Init class in > every TU which included to ensure it is std::cout etc. > is initialized, but thanks to Patrick work on some targets (which have > init_priority attribute support) it is now initialized only inside of > libstdc++.so.6/libstdc++.a. > > This causes a problem if people do something that has never been supported, > try to run GCC 13 compiled C++ code against GCC 12 or earlier > libstdc++.so.6 - std::cout etc. are then never initialized because code > including expects the library to initialize it and the library > expects code including to do that. > > The following patch is second attempt to make this work cheaply as the > earlier attempt of aliasing the std::cout etc. symbols with another symbol > version didn't work out due to copy relocation breaking the aliases appart. > > The patch forces just a _ZSt21ios_base_library_initv undefined symbol > into all *.o files which include and while there is no runtime > relocation against that, it seems to enforce the right version of > libstdc++.so.6. /home/jakub/src/gcc/obj08i/usr/local/ is the install > directory of trunk patched with this patch, /home/jakub/src/gcc/obj06/ > is builddir of trunk without this patch, system g++ is GCC 12.1.1. > $ cat /tmp/hw.C > #include > > int > main () > { > std::cout << "Hello, world!" << std::endl; > } > $ cd /home/jakub/src/gcc/obj08i/usr/local/bin > $ ./g++ -o /tmp/hw /tmp/hw.C > $ readelf -Wa /tmp/hw 2>/dev/null | grep initv > 4: 0000000000000000 0 FUNC GLOBAL DEFAULT UND > _ZSt21ios_base_library_initv@GLIBCXX_3.4.32 (4) > 71: 0000000000000000 0 FUNC GLOBAL DEFAULT UND > _ZSt21ios_base_library_initv@GLIBCXX_3.4.32 > $ /tmp/hw > /tmp/hw: /lib64/libstdc++.so.6: version `GLIBCXX_3.4.32' not found > (required by /tmp/hw) > $ LD_LIBRARY_PATH=/home/jakub/src/gcc/obj08i/usr/local/lib64/ /tmp/hw > Hello, world! > $ > LD_LIBRARY_PATH=/home/jakub/src/gcc/obj06/x86_64-pc-linux-gnu/libstdc++-v3/src/.libs/ > /tmp/hw > /tmp/hw: > /home/jakub/src/gcc/obj06/x86_64-pc-linux-gnu/libstdc++-v3/src/.libs/libstdc++.so.6: > version `GLIBCXX_3.4.32' not found (required by /tmp/hw) > $ g++ -o /tmp/hw /tmp/hw.C > $ /tmp/hw > Hello, world! > $ > LD_LIBRARY_PATH=/home/jakub/src/gcc/obj06/x86_64-pc-linux-gnu/libstdc++-v3/src/.libs/ > /tmp/hw > Hello, world! > $ LD_LIBRARY_PATH=/home/jakub/src/gcc/obj08i/usr/local/lib64/ /tmp/hw > Hello, world! > > Bootstrapped/regtested on x86_64-linux, i686-linux and > sparc-sun-solaris2.11 > > On the last one I've actually checked a version which had > defined(_GLIBCXX_SYMVER_SUN) next to defined(_GLIBCXX_SYMVER_GNU), but > init_priority attribute doesn't seem to be supported there and so I > couldn't > actually test how this works there. Using gas and Sun ld, Rainer, does one > need to use gas + gld for init_priority or something else? > > Ok for trunk and after a while for GCC 13.2? > Yes, for both, thanks for the fix. After it lands on the gcc-13 branch I'll also update the manual with: --- a/libstdc++-v3/doc/xml/manual/abi.xml +++ b/libstdc++-v3/doc/xml/manual/abi.xml @@ -275,6 +275,7 @@ compatible. GCC 11.1.0: libstdc++.so.6.0.29 GCC 12.1.0: libstdc++.so.6.0.30 GCC 13.1.0: libstdc++.so.6.0.31 + GCC 13.2.0: libstdc++.so.6.0.32 Note 1: Error should be libstdc++.so.3.0.3. > > 2023-04-28 Jakub Jelinek > > PR libstdc++/108969 > * config/abi/pre/gnu.ver (GLIBCXX_3.4.32): Export > _ZSt21ios_base_library_initv. > * testsuite/util/testsuite_abi.cc (check_version): Add > GLIBCXX_3.4.32 > symver and make it the latestp. > * src/c++98/ios_init.cc (ios_base_library_init): New alias. > * acinclude.m4 (libtool_VERSION): Change to 6:32:0. > * include/std/iostream: If init_priority attribute is supported > and _GLIBCXX_SYMVER_GNU, force undefined > _ZSt21ios_base_library_initv > symbol into the object. > * configure: Regenerated. > > --- libstdc++-v3/config/abi/pre/gnu.ver.jj 2023-04-20 > 09:36:09.415371050 +0200 > +++ libstdc++-v3/config/abi/pre/gnu.ver 2023-04-27 17:58:44.599675359 +0200 > @@ -2514,6 +2514,10 @@ GLIBCXX_3.4.31 { > > } GLIBCXX_3.4.30; > > +GLIBCXX_3.4.32 { > + _ZSt21ios_base_library_initv; > +} GLIBCXX_3.4.31; > + > # Symbols in the support library (libsupc++) have their own tag. > CXXABI_1.3 { > > --- libstdc++-v3/testsuite/util/testsuite_abi.cc.jj 2023-01-16 > 11:52:17.495713257 +0100 > +++ libstdc++-v3/testsuite/util/testsuite_abi.cc 2023-04-27 > 17:30:39.651173917 +0200 > @@ -213,6 +213,7 @@ check_version(symbol& test, bool added) > known_versions.push_back("GLIBCXX_LDBL_3.4.29"); > known_versions.push_back("GLIBCXX_3.4.30"); > known_versions.push_back("GLIBCXX_3.4.31"); > + known_versions.push_back("GLIBCXX_3.4.32"); > known_versions.push_back("GLIBCXX_LDBL_3.4.31"); > known_versions.push_back("GLIBCXX_IEEE128_3.4.29"); > known_versions.push_back("GLIBCXX_IEEE128_3.4.30"); > @@ -251,7 +252,7 @@ check_version(symbol& test, bool added) > test.version_status = symbol::incompatible; > > // Check that added symbols are added in the latest pre-release > version. > - bool latestp = (test.version_name == "GLIBCXX_3.4.31" > + bool latestp = (test.version_name == "GLIBCXX_3.4.32" > // XXX remove next 2 lines when baselines have been regenerated. > || test.version_name == "GLIBCXX_IEEE128_3.4.31" > || test.version_name == "GLIBCXX_LDBL_3.4.31" > --- libstdc++-v3/src/c++98/ios_init.cc.jj 2023-01-16 > 11:52:16.995720625 +0100 > +++ libstdc++-v3/src/c++98/ios_init.cc 2023-04-27 18:34:46.121276617 +0200 > @@ -199,5 +199,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > return __ret; > } > > +#ifdef _GLIBCXX_SYMVER_GNU > + void ios_base_library_init (void) > + __attribute__((alias ("_ZNSt8ios_base4InitC1Ev"))); > +#endif > + > _GLIBCXX_END_NAMESPACE_VERSION > } // namespace > --- libstdc++-v3/acinclude.m4.jj 2023-02-02 09:53:31.745525704 +0100 > +++ libstdc++-v3/acinclude.m4 2023-04-27 17:27:51.071626279 +0200 > @@ -3841,7 +3841,7 @@ changequote([,])dnl > fi > > # For libtool versioning info, format is CURRENT:REVISION:AGE > -libtool_VERSION=6:31:0 > +libtool_VERSION=6:32:0 > > # Everything parsed; figure out what files and settings to use. > case $enable_symvers in > --- libstdc++-v3/include/std/iostream.jj 2023-01-16 > 11:52:16.968721023 +0100 > +++ libstdc++-v3/include/std/iostream 2023-04-27 18:34:07.479837226 +0200 > @@ -77,6 +77,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > // in the compiled library instead (src/c++98/globals_io.cc). > #if !__has_attribute(__init_priority__) > static ios_base::Init __ioinit; > +#elif defined(_GLIBCXX_SYMVER_GNU) > + __extension__ __asm (".globl _ZSt21ios_base_library_initv"); > #endif > > _GLIBCXX_END_NAMESPACE_VERSION > --- libstdc++-v3/configure.jj 2023-02-02 09:53:31.795524981 +0100 > +++ libstdc++-v3/configure 2023-04-27 17:29:13.263429963 +0200 > @@ -68652,7 +68652,7 @@ $as_echo "$as_me: WARNING: === Symbol ve > fi > > # For libtool versioning info, format is CURRENT:REVISION:AGE > -libtool_VERSION=6:31:0 > +libtool_VERSION=6:32:0 > > # Everything parsed; figure out what files and settings to use. > case $enable_symvers in > > Jakub > >